1. Field of the Invention
The present invention relates generally to manufacture of heads for data storage devices and more specifically to a write head for a hard disk drive.
2. Description of the Prior Art
As the areal density of storage media steadily increases and track widths become narrower and closer together, there is more and more chance of interference from adjacent tracks. This interference has become so common that the acronym “ATI” for Adjacent Track Interference has been coined. This interference naturally increases write and read errors and is therefore undesirable.
A typical read/write head 14 is shown in FIG. 4, which is a side cut-away view of the slider 16 shown in FIG. 3. The magnetic head 14 includes a coil 18, P1 pole 20, and a second pole P2 22 which is separated from P1 pole 20 by write gap 23. The P1 pole 20, second pole P2 22 and write gap 23 can be considered together to be included in the write head 26. Magnetic flux is induced when current is passed through the coil 18 and then passes through the tip of the P2 22 pole, across the gap 23, through the recording medium (not shown) and returns through the P1 pole 20 to complete the magnetic circuit. The magnetic flux thus acts to write data to the magnetic medium.
Magnetic flux flows in lines which are not straight, and thus tend to spread out slightly as they traverse the gap 23 separating the poles P1 20 and P2 22. The amount of “spread” produced depends on the shape and configuration of the poles P1 20 and P2 22. FIG. 5 (prior art) shows a typical write head of the prior art including poles P1 20 and P2 22 and gap 23. It is common practice that the P1 pole 20 actually be composed of 2 or more layers, which in the example shown are two layers, designated as N1 42 and N3 44. It is common practice that the N1 42 layer be configured to be approximately the width of the P2 pole 22 and gap 23, and the N1 42 layer having a straight portion 43 having a thickness of generally is approximately 2-4 times the thickness of the gap layer 23. For ease of viewing, there has been no attempt to make the relative thicknesses of the layers in proper proportion.
The N3 layer 44 is typically much wider than the N1 layer 42, and the N3 layer 44 is also typically slightly beveled to channel magnetic flux more easily. The bevel angle α 46 is shown in the figure and generally is in the range of 5-15 degrees.
The magnetic flux 48 is shown spreading out as it leaves the P2 pole 22 until it finally contacts the N3 layer 44 of the P1 pole 20. This spread establishes the ATI. It is evident that this ATI is much wider than the P2 pole 22, and thus undesirable.
The design of write heads in general is a balance between narrowing undesirably broad ATI and having poles broad enough to allow adequate magnetic flux flow so that there is good field strength to accomplish satisfactory write or overwrite of data. As track widths become narrower and narrower, this balance becomes ever more delicate.
Thus there is a need for a magnetic write head which has smaller magnetic flux spread, thus creating less ATI, while allowing good magnetic flux channeling for good write and overwrite of data.